The present invention relates to an improved case for a magnetic tape cassette case, and more particularly to the structure of a magnetic tape cassette case of a type which covers five walls of a magnetic tape cassette.
Recently, video tape recorders, 8-mm video cameras, computers, and word processors have been extensively used. In this connection, magnetic tape cassettes or magnetic disk o cassettes are employed as data recording media for such devices. Magnetic tape cassettes are preferably placed in cassette cases when stored. Some cassette cases are designed so that two halves of the case can be opened and closed in a hinged manner. On the other hand, rectangular-box-shaped cases are employed for certain magnetic tape cassettes, for example, those intended for use in VHS-type video cameras, Beta-type video cameras, and 8-mm video cameras due to their simple construction and convenience in use.
As is well known in the art, a cassette case is used not only for purposes of merely storing and conveniently stacking magnetic tape cassettes, but also for protecting the magnetic tape cassette from damage and for preventing entrance of dust, more specifically, for preventing the accumulation of dust on the magnetic tape or on the inner surface of the cassette.
As described above, one of the important functions of a magnetic tape case is to protect the magnetic tape cassette and the tape inside. In addition, it is also important that the magnetic tape cassette case be designed so that the magnetic tape cassette can be inserted into the case and removed therefrom with ease; for instance, it is important that the inner surfaces of the case be smooth so that the cassette can be easily slid in and out of the case. However, if the inner surfaces of the case are formed in this manner, when the cassette case is held so that its opening is at the bottom, and especially when the case is shaken in such a state, the magnetic tape cassette is liable to fall out of the case under its own weight, possibly damaging the cassette.
Japanese Unexamined Published Utility Model Applications Nos. 64682/1988, 111477/1988 and 111478/1988 disclose countermeasures which may be taken in response to the above-described difficulty. That is, in order to prevent the cassette from dropping from the case, as shown in FIG. 5, protrusions a or locking pieces can be formed on the inner surfaces of side walls near the edges which define opening 22 of a cassette case 20 through which the cassette is inserted and removed, more specifically, on the inner surfaces of the right and left walls 21 and 21 near their edges.
In another structure for preventing the magnetic tape cassette from dropping from the cassette case, the protrusions a are not used, and instead an elongated elastic locking piece b is employed as indicated by the phantom lines in FIG. 5. That is, the locking piece b is bonded to an inner surface of the cassette case in such a manner that it is elastically inwardly curved. In addition, the manufacturing tolerance on the width L.sub.1 of the opening 22 is severe with respect to the width of the cassette (L.sub.1 being smaller than the rear end dimension L.sub.0 of the case).
In manufacturing a cassette case having the protrusions a or locking piece b, it is necessary to provide a manufacturing step for mounting these members. In manufacturing the above-described cassette case 20, an intermediate product, namely, a blank plate formed by blanking a plate of synthetic resin or cardboard, is folded and formed into the cassette case. However, it may be required to stack the intermediate products prior to use by stacking them one on another. It is rather difficult to do so though because the intermediate products have the protrusions a or locking pieces b. For the same reason, the intermediate products are not suitable for conveyance by an automatic feeder. That is, it is quite troublesome to handle the intermediate products, which greatly lowers the productivity of the cassette case.